Detailed entry information

Ser/Thr-kinase component of cyclin D-CDK4, DC complexes that phosphorylate and inhibit members of the retinoblastoma, RB protein family including RB1 and regulate the cell-cycle during G(1/S transition. Phosphorylation of RB1 allows dissociation of the transcription factor E2F from the RB/E2F complexes and the subsequent transcription of E2F target genes which are responsible for the progression through the G(1 phase. Hypophosphorylates RB1 in early G(1 phase. Cyclin D-CDK4 complexes are major integrators of various mitogenenic and antimitogenic signals. Also phosphorylates SMAD3 in a cell-cycle-dependent manner and represses its transcriptional activity. Component of the ternary complex, cyclin D/CDK4/CDKN1B, required for nuclear translocation and activity of the cyclin D-CDK4 complex. {ECO:0000269|PubMed:15241418, ECO:0000269|PubMed:18827403, ECO:0000269|PubMed:9003781}.

Subcellular location

Cytoplasm. Nucleus. Membrane. Note=Cytoplasmic when non-complexed. Forms a cyclin D-CDK4 complex in the cytoplasm as cells progress through G(1 phase. The complex accumulates on the nuclear membrane and enters the nucleus on transition from G(1 to S phase. Also present in nucleoli and heterochromatin lumps. Colocalizes with RB1 after release into the nucleus.